Using 'sniffer' cell biosensors， we evaluated the effects of specific firing patterns and frequencies on activity-dependent somatodendritic release of vasopressin from paraventricular nucleus neurones. Somatodendritic release of vasopressin was rarely observed during continuous firing but was strengthened by clustered activity. Moreover， release evoked at any given frequency was robustly potentiated by NMDA receptor (NMDAR)-mediated firing. Differently from axonal release， NMDAR activation was necessary for somatodendritic release to occur at physiological firing frequencies， acting thus as a gating mechanism by which activity-dependent release from these two neuronal compartments could be independently... More
Using 'sniffer' cell biosensors， we evaluated the effects of specific firing patterns and frequencies on activity-dependent somatodendritic release of vasopressin from paraventricular nucleus neurones. Somatodendritic release of vasopressin was rarely observed during continuous firing but was strengthened by clustered activity. Moreover， release evoked at any given frequency was robustly potentiated by NMDA receptor (NMDAR)-mediated firing. Differently from axonal release， NMDAR activation was necessary for somatodendritic release to occur at physiological firing frequencies， acting thus as a gating mechanism by which activity-dependent release from these two neuronal compartments could be independently regulated. The NMDAR-mediated potentiation was independent of a specific firing pattern and was not accompanied by increased spike broadening， but correlated with higher dendritic Ca levels. Our studies provide fundamental novel information regarding stimulus-secretion coupling at somatodendritic compartments， and shed light into mechanisms by which activity-dependent release of neuronal signals from axonal terminals and dendrites could be regulated in a spatially compartmentalized manner.
